The overall purpose of this research proposal is to examine the role of the limbic system and cortically related structures in hypothalamic aggression. The first phase of the research project attempts to determine how the limbic system and cortically related structures modulate attack behavior elicited by electrical stimulation of the hypothalamus. The principal paradigm involves presentation of paired trials of single (hypothalamic) and dual (limbic plus hypothalamic) stimulation. Differences in response latency between paired trials of single and dual stimulation provide the basis for determining the effects of limbic stimulation upon hypothalamic attack behavior. The limbic structures thus far considered include the hippocampus, septal area, cingulate gyrus, pyriform cortex and the frontal lobe. A second of this project will attempt to determine the neuroanatomical projections of those structures producing modulating effects upon attack behavior. Methods for studying these neuronal connections include: silver impregnation methods of degenerating axons and their terminals, autoradiography, and horseradish peroxidase histochemistry. A third phase will attempt to determine the neurophysiological relationships between those structures producing modulating effects upon attack behavior and their target nuclei as determined by neuroanatomical methods. BIBLIOGRAPHIC REFERENCES: Siegel, A., H. Edinger, and M. Dotto. Effects of electrical stimulation of the lateral aspect of the prefrontal cortex upon attack behavior in the cat. Brain Research, 93: 473-484 (1975). Edinger, H., A. Siegel, and R. Troiano. Effect of stimulation of prefrontal cortex and amygdala on diencephalic neurons. Brain Research, 97: 17-31 (1975).